Crystal engineering’s own handyman
One of distinguished professor Len Barbour’s happy places is a well-appointed basement workshop in the De Beers Building on Stellenbosch University’s (SU’s) main campus.
Here, he builds equipment to use in his world-class research projects in the field of supramolecular materials chemistry. More specifically, he and others in the Barbour Group in SU’s Department of Chemistry and Polymer Science study how to design and use porous crystalline materials as minute ‘storage units’ for fluids or gases.
Barbour’s craftsmanship and self-taught toolmaking, mechatronics and software prowess have all contributed to him receiving his fourth A-rating from the National Research Foundation in 2022.
New knowledge rewarded
Barbour believes in “creating new knowledge rather than merely producing new data to support existing knowledge”. More than half of his 227 papers were published in the top 1% of the world’s scientific journals, and he has been cited over 16 000 times.
His work serves as the basis for research being conducted by groups across the globe, and he holds four patents.
He has been awarded the Royal Society of South Africa’s John FW Herschel Medal (2020), a SU Chancellor’s Award for Research (2017), the South African Chemical Institute Gold Medal (2014) and the SASOL Innovator of the Year Award (2013).
In 2013, he completed a DSc in Chemistry at SU.
The happy tinkerer
In 2005, Barbour designed an environmental gas cell, and proceeded to build it in his basement workshop.
The miniature glass-and-valve tube looks deceptively simple but is a mechanical engineering feat. It controls the environment around a crystal placed inside it, making it possible to analyse the crystal’s molecular structure under gas pressure at the atomic level – something that is otherwise very tricky.
“The technique is fairly unique to our lab. There are others, but this one is easier to use routinely.”
Similar devices are available at high-tech synchrotron facilities, but they are rarely found in home-based diffraction laboratories such as Barbour’s.
“Labs from first-world countries often send us crystals to analyse.”
Barbour has since improved the design of the environmental gas cell. Currently, he is working on new ideas to allow for measurements of crystals to be taken at different temperatures and humidity levels, not merely at room temperature under normal atmospheric pressure.
This part-time tinkerer once purchased a differential scanning microcalorimeter, which is used to characterise the molecular structure and stability of a material. He then took it apart, improved on the design of its pressure cell, and developed software to more consistently control the introduction of gas over time.
In the process, his team developed the pressure-gradient differential scanning calorimetry (PG-DSC) technique, which they and other groups now use to qualitatively assess flexibility in porous materials. It constitutes a simpler, more reliable method than the standard ones used to directly measure the heat of sorption (the process by which one substance becomes attached to another).
“Instead of just focusing on chemistry and wishing someone would develop a certain piece of equipment, I do so myself. I can then get it to work the way I want to, and much quicker at that.”
Sharing self-made solutions
This can-do attitude reflects Barbour’s positive take on life, and his supreme ability to find solutions when problems arise.
For his PhD (obtained in 1994 from the University of Cape Town), he constructed new equipment to analyse and measure the amount and rate of interaction between a gas or vapor and a material – a technique called ‘gravimetric sorption’.
Barbour taught himself how to write software that monitors, controls and automates custom-built, computer-based instruments.
Nowadays, relevant commercial instruments and software are for sale, but this was not the case in South Africa in the 1990s. Data processing and the theory behind it were also poorly developed, which explains Barbour’s DIY approach.
He went on to write the freeware ‘X-Seed’, an interface that allows users to visualise, understand and illustrate the arrangements or packing of molecules in crystalline solids. One of his subsequent crystallographic images was even featured on the cover of Science in 1999.
“I wrote X-Seed for myself because I thought there had to be a better way to do it. Then others liked it, and I just distributed it.”
Researchers worldwide still use it. As such, Barbour keeps it updated.
It is this freeware that enabled his discovery of interstitial voids in crystals, a topic on which he published two papers in Science, among other journals. The unconventional porosity of crystals with interstitial voids in due course rekindled his interest in dynamic sorption materials, a major focus of his current research.
At the time, Barbour was a research assistant professor at the University of Missouri Columbia, where he spent a fruitful decade after 1994. His work there included, among other things, postdoctoral research on some of the most significant early developments in the supramolecular chemistry of encapsulating or confining large molecules inside the cavity of a molecular host.
The Stellenbosch years
Barbour relocated from the US to start work at SU in 2003. In 2007, he received one of the first 21 South African Research Chair Initiative (SARChI) grants.
He has since built up strong cooperative links with colleagues Profs Catharine Esterhuysen and Delia Haynes. The trio shares research facilities, student supervision and ideas.
“The infrastructure we have built up here is really world class.”
Barbour reflects on this: “That’s something that our students often do not realise until they leave here. They think that if it’s like this in South Africa, it must be even better in the UK. Then they leave, and realise they were better off at Stellenbosch in terms of access to state-of-the-art equipment.
“Essentially, we have everything here needed to do our research. And if it’s not, and we can’t buy it, it becomes part of the research, and we build it.”
Crystals to combat climate change
Two decades ago, people thought porous crystalline materials could be used to store hydrogen fuel. These days, research groups worldwide are considering their use in combatting climate change.
“People talk about how they want to capture CO2 from the air, store it in these materials and bury it underground. I might be proven wrong, but my feeling is that such materials are not good for the large-scale storage of gases. Suitable materials are still very costly to produce. You’d need vast quantities and lots of money for this to work.
“We [Visser, Esterhuysen and Haynes] work with porous materials called ‘metal-organic frameworks’. We try to make them very selective, with very high capacities and very large pores. We can’t yet compete in price against much cheaper – albeit less selective – carbon and zeolites.”
Barbour believes porous materials such as the latter two could be better used to improve separation and catalysis technology, which would bring down the energy cost involved in, for instance, separating nitrogen from air.
“The ancient Egyptians already knew that carbon cleans water and sanitises wounds because of its porous properties. In the 1900s, people started studying porous materials scientifically, but, for the longest time, mostly worked on activated carbon and zeolite, a product which you may find in cat litter or detergents.
“Carbon and zeolites are very cheap and perform reasonably well. Now that we have more insights into porous materials, we can make ones with vastly improved properties. Although scaling them up for commercial use isn’t viable yet, the price will come down as demand increases.
“For now, we are still doing the fundamental research.”
Prof Len Barbour
Photo by Stefan Els
Written by Engela Duvenage